This invention relates to a toner application method for developing electrostatic latent images with a toner and a developer composition therefor.
Conventionally, various types of apparatus have been proposed and put into practice as a dry type one-component developer apparatus. However, in any of those types, it has been very difficult to form a thin layer of one-component dry developer, sg that a relatively thick layer of the developer is used. On the other hand, the recent desire for the improved sharpness, resolution or other qualities of developed images has necessitated the achievement of a system for forming a thin layer of one-component dry developer.
A method of forming a thinlayer of one-component dry developer has been proposed in Japanese Laid-Open Patent application No. 43037/1979 and has been put into practical use. However, this method is directed to the formation of a thin layer of a magnetic developer, not of a non-magnetic developer. The particles of a magnetic developer must each contain a magnetic material in a large proportion to gain a magnetic property. This is disadvantageous since it results in poor image fixing characteristic when the developed image is heat-fixed on a recording paper to be transfer-printed. Further, because the magnetic material is generally black or dark-brown in color, it is difficult to obtain a clear color image by using a magnetic toner. As employed herein the phrase "in the range of 150 to 250 mesh" refers to a mass of magnetic particles passing a sieve of 150 mesh and not passing a sieve of 200 mesh; "100 to 150 mesh " and "200 to 250 mesh" refers to particles passing a sieve of 100 mesh or 200 mesh, but not 150 mesh or 250 mesh, respectively; "under 250 mesh" means a mass of particles passing through a sieve of 250 mesh; and "over 100 mesh" means a mass of particles not passing a sieve of 100 mesh.